Ships and offshore floating bodies operate in the ocean over a long period of time, while storms and even typhoons occur frequently in the ocean, and thus storm attacks are the greatest threat to ships and offshore floating bodies. Every year, disasters such as casualties, property loss and water pollution, which are caused by failure of ships and floating bodies to escape from storms and typhoons, are countless. At present, the main approaches adapted to prevent disasters for ships and floating bodies, are simply avoiding, or enhancing the anchoring systems. The fundamental dilemma for these technologies is that the ocean provides formidable engineering challenges which must be solved to ensure survivability in extreme conditions, such as Typhoons, and provide robust, reliable and low-cost solution.
When a storm comes, not every ship can find a suitable area to avoid the storm; for conventional catenary anchoring systems, the chains will be quickly straightened in the storm. In long periodic waves, if a ship keeps moving away as following the waves in the storm, the huge kinetic energy generated by the movement of the ship cannot be depleted, resulting in dragging anchor or chain breakage, and subsequently the ship being out of control and disasters. Some ships and floating bodies have increased the chain diameter, adapted more chains, or enhanced the anchor structure, all of which are for the purpose of increasing the minimum break load; these solutions have enhanced the anchoring system with huge anchoring costs, but do not fundamentally change the possibility of the ships being destroyed in the storms or even typhoons. Under the action of ocean currents and long periodic waves, the chains with buffering capacity are stretched by the ocean currents, and the inextensible anchor chain still faces the threat of being straightened to break by the long periodic waves in typhoon. Some immobile floating platforms have introduced ropes with greater flexibility for anchoring, or introduced weights and pontoons to the anchoring system, in order to increase the elastic links in the anchoring system; the above solutions alleviate the problem of lacking elasticity of anchoring system, however, as the moving distance of the floating body increases, the effective buffering capacity of the elastic links are depleted to finally reach a rigid state, and thereby the anchoring system still faces the threat of dragging anchor or anchoring line breakage. Also, since the anchoring force and the chain retraction of the floating platform are opposite in direction but equal in magnitude, the force on the floating structure increases as the anchoring force increases, which is a huge threat to the safety of the structure itself; the excessive force on the structure can cause structural failure of the ships and floating platforms or ship sinking. Therefore, the problem that which anchoring solution shall be adapted to enable ships and floating bodies to survive in storms or even typhoons has not been effectively addressed.
The major cause of ships and floating bodies frequently suffering from damages is that, under the action of wind, ocean currents and long periodic waves, neither the conventional catenary systems with only anchor chains nor the improved anchoring systems with introduced elastic links can change the fact that, they will be straightened due to their limitation in length and elasticity, resulting in a rapidly increasing anchoring tension which will exceed the breaking value of the anchoring material and cause fracture and failure of the anchoring system, and thereby accidents of ships and floating bodies, such as shifting, grounding or crashing will occur. In addition, an excessively enhancing anchoring system also increases the force on the ship or the floating structure in the storm, which will increase the probability of local damage to the ship or the floating body.